Tyrannosaurus (Greek: τυραννος σαυρος, "tyrant lizard") was a species of dinosaur known from several specimens found in North America and Asia. One of the largest carnivorous animals to have walked the earth, Tyrannosaurus has, since its late-19th century discovery, become the most famous as well, the subject of serious science as well as a perennial character in books, film, and television.

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Description

Tyrannosaurus was a large theropod, with recovered specimens averaging between 36-40 feet in length and standing about 12 feet at the hips [1]. The weight of an adult has been estimated to be between 5-7 tons, roughly comparable to a living African elephant.

The skull was massively-built and robust. The sixty teeth which lined the mouth were up to 7-inches long and banana-shaped, with cutting serrations on each edge. Tyrannosaurus also had forward-facing eyes, giving it binocular vision. The other noticeable feature was the small forearms bearing only two clawed fingers, which many scientists have declared useless or vestigial. But the shoulder blades were relatively-large, indicating the arms were still well-muscled, and it has been postulated that these arms aided Tyrannosaurus in lifting itself up on its hind feet from a prone position.[2]

Species

Three species have been identified as belonging in the genus Tyrannosaurus:

Tyrannosaurus lanpingensis

First identified in 1975, from Jingxing Formation of Yunnan, China.

Tyrannosaurus rex

Type species; originally found (as fragments) in 1874 near Golden, Colorado, with more complete finds beginning in 1892.

Tyrannosaurus torosus

Discovered in 1921 in Alberta, Canada by Charles Sternberg, it was originally named Daspletosaurus[3]. G. S. Paul in 1988 added this animal to the Tyrannosaurus genus[4].

Diet

Some scientists, notably Dr. Jack Horner[5][6] of the Museum of the Rockies in Bozeman, Montana, have put forward the hypothesis that Tyrannosaurus was exclusively a scavenger. They cite as their evidence the relatively-slow estimated speed of the animal - no more than 15 miles per hour - as well as the small forelimbs and the large olfactory casts made inside their skulls, which indicated a powerful sense of smell. This may be partially true, since most carnivores today will happily scavenge available meat. However, it probably was not an exclusive scavenger, as most meat-eaters must also hunt in order to survive. Tyrannosaurus' jaws were also quite adaptive to grabbing live prey. In opposition to the scavenger theory there are several specimens of dinosaur - principally Edmontosaurus and Triceratops - in North American museums which show clear bite wounds that have healed over, and tyrannosaur teeth easily fit inside them.[7][8]

Bite strength

Recent estimates based on computer models, scale models of skulls, and comparisons with living animals suggest Tyrannosaurus had one of the most powerful bites of any animal. Experiments conducted by Dr. Gregory Erickson when he was a graduate student at the University of California (Berkeley) determined that a minimum of 1,440 pounds of pressure from its front teeth alone could put a 11.5 mm-deep hole in bone, while 3,011 pounds of pressure came from its back teeth[9][10][11][12]. The strength of the bite may have been as much as four tons or more, according to Dr. Eric Snively of the University of Alberta, who discovered the significance of fused nasal bones unique to Tyrannosaurus. "Fused, arch-like nasal bones are a unique feature of tyrannosaurids," he said. "This adaptation, for instance, was keeping the T. rexes from breaking their own skull while breaking the bones of their prey." A fused nasal bone channels the force of the bite from the skull to the prey item; this, with the combination of extremely-powerful neck muscles, convinced Dr. Snively and his colleagues that an adult Tyrannosaurus could potentially use 200,000 newtons of force when pulling meat off a carcass. [13]

In 1995 a coprolite (fossilized dung) was discovered near Eastend, Saskatchewan, and determined to have been from a tyrannosaur based on the size as well as the bone fragments within from a Triceatops, leading scientists to speculate that the power of a T-rex bite could shatter bone.[14]

Fossils

The earliest find of a Tyrannosaurus fossil occurred in 1892. In 1905, after additional discoveries of fossils, the president of the American Museum for Natural History named the dinosaur. Since then, more than 30 specimens have been found.

In 1990, amateur paleontologist Susan Hendrickson discovered the most complete Tyrannosaurus fossil yet. The fossil, named "Sue", is also one of the largest tyrannosaur specimens discovered.[15]

Paleontologist Mary Schweitzer has discovered unfossilized soft tissue in a tyrannosaur skeleton. This was unexpected as tissue was not known to stay unfossilized for 65 million years. Evolutionists saw this as evidence that tissue can last that long, while creationists saw it as evidence that the fossils were not that old.[16][17]

Evolutionary scientists believe that Tyrannosaurus lived at the end of the Cretaceous period, dated to approximately 65 million years ago, and that modern birds are the descendants of dinosaurs such as T. rex. [18][19]

References

↑Brochu, C.R. 2003. Osteology of Tyrannosaurus rex: insights from a nearly complete skeleton and high-resolution computed tomographic analysis of the skull. Memoirs of the Society of Vertebrate Paleontology. 7: 1-138.